A power supply that is often used in telecommunications, transportation, industry and other applications may require electrical isolation between an input and an output of the power supply. A transformer with a primary winding and a secondary winding is often used to provide this isolation. Furthermore, the power supply may further include a switching element and a rectifying diode connected to the secondary winding.
FIG. 1 is a diagram which shows a schematic illustration of a power supply and a device for controlling the power supply in the prior art. As shown in FIG. 1, a power supply 100 is used to convert a first voltage (Vin, such as a direct current voltage or direct voltage) into a second voltage (Vo, such as a direct current voltage or direct voltage). The power supply 100 may include a switching element 101, a transformer 102 with a primary winding 1021 and a secondary winding 1022, a rectifying diode 103 connected to the secondary winding 1022.
As shown in FIG. 1, a device 110 for controlling the power supply 100 may include a source voltage terminal 111 (for example it is referred to as VCC), a feedback terminal 112 (for example it is referred to as FB), and a driving terminal 113 (for example it is referred to as DRV) for driving the switching element 101. An on/off operation of the switching element 101 may be controlled by a driving signal from the driving terminal 113 with a pulse width modulation (PWM).
As shown in FIG. 1, the feedback terminal 112 may connect to a drain electrode of the switching element 101 and may be configured to be inputted a feedback signal from the drain electrode of the switching element 101. Furthermore, the feedback terminal 112 may connect to an auxiliary winding in a side of the primary winding, this may be referred to as a structure of primary side regulation (PSR); or the feedback terminal 112 may connect to an optical coupler in a side of the secondary winding, this may be referred to as a structure of secondary side regulation (SSR).
This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.